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TABLE OF CONTENTS. 



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on the subject, 495 ; Julikn does Liu; saiiu;, 495 ; bolli these writers show by 

 their writings tliat tliey have inadii no investigation of the faets, 495. Swket^ 

 in 1876, on a HUi)])osed niiconforniabilily of the Huronian and Laurentiaii at 

 Penokoc Gap, 495, 496 ; luViNG on the same, 496 ; nature of such occurrences 

 not understood by the Wiscou.siu geologists, 496. IiiviNO on the lluronia.u in 

 "Wisconsin, 497 ; his ignorance of the necessary results of the intrusion of an 

 eruptive into a sedimentary cue, 497 ; Irving adopts some of Wadsworth's 

 lithoh)gical views, but omits to state the source from which thev were derived, 

 497, 498. Hall, in 1866, refers the gneiss and granite of Redwood liiver to 

 the Laureiitian, and some quartzites in Minnesota to the lluronian, 498 ; 

 Hall's views opposed by IIaylln and N. H. Winoiiell. The cupriferous 

 roelcs on Lake Superior, within tiic limits of Minnesota, referred to the Potsdara, 

 in 1880, by N. H. Winciiell, 498. 



Tlll^: FOKTIETII PARALLEL SURVEY. 



AVhat rocks are included in the " Archrean" by the Fortieth Parallel geologists, 499, 

 500. The Azoic or Arch^v-an rocks of the Laramie Range, 500; Zirkel's 

 distinctive characters of eruptive and scdimciitary granites, 500, 501 ; defect of 

 las methods, 501 ; King's and A. llACiUE's statements at variance with eaeli 

 other, 501. The Medicine Bow Range referred to the Huronian by A. Hague, 

 602 ;*no proof given that it is ohhir than Tertiary, 502; defects of observation, 

 502. The Uinta Range, 503. The Wahsatch Range, gradual change of views 

 in regard to its age, as volume succeeded volume, 503-507- Conllieting state- 

 ments of ZiRKEL and King, 507, 508. Criticism of KiX(;'s statements, and of 

 his manner of observing, 508 ; similar criticisms by Geikie, 509, 510. Sum- 

 ming up of tlu; results of the Eortieth Parallel Survey, and indication of their 

 value, 510, 511. 



HAYDEN'S SURVEY. 



The rocks of the Chugwater, in 1868, called Laurentian, but no reasons given for this, 



511, 512 ; IIayden, in 18(59, states his theoretic views in regard to igneous and 

 metamorphic rocks, 512. Haydkn caRs the rocks on tlie north side of the Uinta 

 Range Silurian and Huronian, 512; tlie Fortieth Parallel Survey calls them 

 Carbonifenms, Powell Devonian, iMinuons Cambrian, and Marsh Silurian, 



512, 513. Endlkui, in 1871, calls all the crystaRinc rocks in the region studied 

 by him, at th'.; head of the Rio Grande and Rio Animas, Metamorphic PaliBozoic, 

 613. Statement of Peale in, regard to crystalline rocks, 513. ENDLrciI divides 

 the Azoic rocks into three systems, 613, 514 ; he admits the insufficiency of his 

 observations, 514. Remarks by St. John and Pkalk, 514. Summing Up of the 

 condition of things in the Rocky Mountains, 514, 515. 



WHEELER'S SURVEY. 



No evidence offered in regard to the Azoic, 515. Stevenson in regard to age of rocks 

 caRed Archaean, in parts of New JMcxico and Colorado, 515. 



